Backplanes are printed circuit boards or metal plates on the upper side of which "daughter" PCBs are detachably mounted perpendicularly to the backplanes for easy removal and replacement while the circuit is still being powered. One way of electrically connecting the daughter boards to other daughter boards, the backplane, and other circuitry is by providing metallized surface portions near the edges of the daughter boards and inserting them between the forked prongs of electrical connectors that are secured to the backplane. Another way of making electrical connection to the daughter boards involves using post and box connectors. The connectors secured to the backplane often have connector posts extending from the lower side of the backplanes for receiving wires connecting selected pairs of posts, and bus bars are often connected to a line of connector posts under the backplane to distribute voltage to a plurality of posts. These connections to the daughter boards are typically designed to carry small amounts of current; thus, a large number of contacts are connected in parallel when large amounts of current are needed.